Leaf spring arrangement

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the priority of German Patent Application, Serial No. 10 2014 101 429.4, filed Feb. 5, 2014, pursuant to 35 U.S.C. 119(a)-(d), the disclosure of which is incorporated herein by reference in its entirety as if fully set forth herein.

BACKGROUND OF THE INVENTION

The present invention relates to a leaf spring arrangement for a motor vehicle axle.

The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention.

It is known in the art to equip motor vehicles with axle systems so that the wheels of the motor vehicle are resiliently supported. At standstill, static wheel loads act on the motor vehicle and are superimposed during operation of the motor vehicle with dynamic wheel loads.

Different axle concepts are known, for example a suspended rigid axle or independent wheel suspensions, in order to realize the desired suspension of the motor vehicle. In principle, the wheel is acted upon by a suspension and an attenuation to absorb the static and dynamic wheel loads. Mechanical springs are especially used hereby and may be designed, for example, as round wire springs or also as leaf springs. In order for the leaf springs to be coupled with the motor vehicle axle components, e.g. with the motor vehicle control arms, in particular transverse control arms, it is known to provide a leaf spring at each end thereof with a mount which can be threadably engaged, for example, to a respective transverse control arm and which is typically screwed to the end of the leaf spring by a bolt received in a throughbore in the leaf spring.

<figref idref="DRAWINGS">FIG. 1</figref> shows a conventional leaf spring <b>1</b> configured as transverse leaf spring <b>2</b>. The transverse leaf spring <b>2</b> has a midsection <b>3</b> and two ends <b>4</b>. A mount <b>5</b> is connected to the each end <b>4</b> of the transverse leaf spring by drilling a bore through the end <b>4</b> of the transverse leaf spring <b>2</b> for passage of a screw bolt <b>6</b> so as to couple the end <b>4</b> to the mount <b>5</b>. The midsection <b>3</b> is further provided with attachments <b>7</b> to connect the transverse leaf spring <b>2</b> to a not-shown motor vehicle body or subframe. A mechanical drilling of the transverse leaf spring <b>2</b> in this way to realize the connection between the mount <b>5</b> and the end <b>4</b> of the leaf spring <b>2</b> adversely affects the durability and life of the leaf spring.

It would be desirable and advantageous to provide an improved leaf spring arrangement which obviates prior art shortcomings and which has a long-lasting life while yet being producible in a simple and cost-effective way and reliable in operation.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, a leaf spring arrangement for a motor vehicle axle includes a leaf spring made of a fiber composite and having ends, each end having a flat underside to provide a joining surface, and mounts for attachment onto an axle component, the mounts being bonded by an adhesive flatly against the underside of the ends of the leaf spring in an area of the joining surface, each mount having an opening for receiving a metallic bearing or screw bolt.

The present invention resolves prior art problems by applying an adhesive to bond the mount to the end of the leaf spring. Examples of an adhesive include a single-component adhesive or two-component adhesive. Currently preferred is the use of an adhesive that can be thermally activated or an anaerobically curable adhesive. The mount has a flat joining surface which complements the flat joining surface at the end of the leaf spring and is bonded thereto via the adhesive to connect the joining surfaces of leaf spring and mount to one another. The bond at the ends of the leaf spring is effective and allows movements by the suspension and thus any changes in shape of the leaf spring in the inner zone or midsection, while the ends of the leaf spring are able to move in kinematic movement direction but not to move within themselves. Thus, the presence of microcracks, in particular in the bonding zone, is effectively prevented in accordance with the present invention.

According to another advantageous feature of the present invention, the mount may be made of a metallic material. Examples include a steel alloy or light metal alloy.

According to another advantageous feature of the present invention, the leaf spring may be configured as a transverse leaf spring. Currently preferred is the provision of a transverse leaf spring which is made of several layers of a fiber composite. An example of a fiber composite includes a fiberglass composite.

According to another advantageous feature of the present invention, the opening of the mount may extend in substantial orthogonal relation to the joining surface and can be used for receiving a bearing or a bolt to enable connection of the mount with a further axle component, e.g. directly with a transverse control arm or connection to a respective control arm of the wheel suspension via a tie rod or pressure bar.

According to another advantageous feature of the present invention, the flat underside of the ends of the leaf spring may be provided in installation direction. The mount with its joining surface rests flatly against the underside and is bonded thereto by a suitable adhesive.

According to another advantageous feature of the present invention, the mount may be configured to embrace, at least in part, an end face of the leaf spring. Advantageously, an adhesive is applied between the end face of the leaf spring and the mount.

According to another advantageous feature of the present invention, a tie rod or pressure bar may be provided and coupled to the mount to exert a force from the mount in a direction of the end of the leaf spring. The bonding zone in particular is thus acted upon by a compressive force or pressing force such that the presence of a shearing is prevented and any movement to undo the bond between the end of the leaf spring and the mount is avoided.

According to another advantageous feature of the present invention, the mount may include a joining surface and a support shoulder configured to extend beyond the joining surface of the mount with respect to a vertical motor vehicle direction, with the support shoulder resting against the end face of the leaf spring.

According to another advantageous feature of the present invention, the support shoulder may have a contact surface which is bonded with the end face of the leaf spring.

The provision of a bonded joint allows a cost-effective and simple production of the leaf spring. Furthermore, in particular the predominantly transmitting force in pressure direction results in a long durability of the leaf spring arrangement according to the present invention with bonded mount.

BRIEF DESCRIPTION OF THE DRAWING

Other features and advantages of the present invention will be more readily apparent upon reading the following description of currently preferred exemplified embodiments of the invention with reference to the accompanying drawing, in which:

<figref idref="DRAWINGS">FIG. 1</figref> shows a conventional transverse leaf spring arrangement;

<figref idref="DRAWINGS">FIG. 2<i>a </i></figref>shows an exploded perspective view of a leaf spring arrangement according to the present invention;

<figref idref="DRAWINGS">FIG. 2<i>b </i></figref>shows a perspective view of the leaf spring arrangement of <figref idref="DRAWINGS">FIG. 2<i>a </i></figref>in assembled state;

<figref idref="DRAWINGS">FIG. 3<i>a </i></figref>shows a schematic illustration of a leaf spring arrangement according to the present invention with attachment of a tie rod; and

<figref idref="DRAWINGS">FIG. 3<i>b </i></figref>shows a schematic illustration of a leaf spring arrangement according to the present invention with attachment of a pressure bar.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Throughout all the figures, same or corresponding elements may generally be indicated by same reference numerals. These depicted embodiments are to be understood as illustrative of the invention and not as limiting in any way. It should also be understood that the figures are not necessarily to scale and that the embodiments are sometimes illustrated by graphic symbols, phantom lines, diagrammatic representations and fragmentary views. In certain instances, details which are not necessary for an understanding of the present invention or which render other details difficult to perceive may have been omitted.

Turning now to the drawing, and in particular to <figref idref="DRAWINGS">FIG. 2<i>a</i></figref>, there is shown an exploded perspective view of a leaf spring arrangement <b>100</b> according to the present invention. The leaf spring arrangement <b>100</b> includes a leaf spring <b>20</b> having opposite ends <b>4</b>. Each end <b>4</b> has an underside <b>8</b> with a flat joining surface <b>9</b> which complements a joining surface <b>10</b> of a mount <b>50</b>. Using an adhesive, the joining surface <b>10</b> of the mount <b>50</b> is bonded to the joining surface <b>9</b>, as shown in <figref idref="DRAWINGS">FIG. 2<i>b</i></figref>. The mount <b>50</b> is provided with an opening <b>11</b> which is arranged below the joining surface <b>9</b>, as viewed in motor vehicle Z direction, indicated by an arrow. The opening <b>11</b> is defined by a longitudinal axis <b>18</b> which extends in orthogonal relation to a longitudinal direction <b>17</b> of the transverse leaf spring <b>2</b> and to the motor vehicle Z direction. With respect to the motor vehicle Z direction, the underside <b>8</b> points downwards. The opening <b>11</b> of each of the mounts <b>50</b> on the opposite ends <b>4</b> of the leaf spring <b>4</b> can be used for receiving a bearing, in particular a metallic bearing, or a screw bolt, for example.

As shown in <figref idref="DRAWINGS">FIG. 2<i>b</i></figref>, the mount <b>50</b> is provided with a support shoulder <b>16</b> which embraces, at least in part, an end face <b>12</b> of the transverse leaf spring <b>20</b> so that the support shoulder <b>16</b> form fittingly rests against the end face <b>12</b>. Advantageously, the support shoulder <b>16</b> is bonded by an adhesive to the end face <b>12</b> of the transverse leaf spring <b>20</b>. The support shoulder <b>16</b> provides a self-centering function with respect to the longitudinal direction <b>17</b> of the transverse leaf spring <b>20</b>, when the mount <b>50</b> is connected to the transverse leaf spring <b>20</b>. During later operation, the transverse leaf spring <b>20</b> undergoes a deflection in motor vehicle Z direction which coincides with a change in length in the longitudinal direction <b>17</b> of the transverse leaf spring <b>20</b>. The applied forces during changes in length in compressive direction are then additionally compensated by the support shoulder <b>16</b>, and the applied forces during changes in length in tensile direction are compensated by the bond between the end face <b>12</b> of the transverse leaf spring <b>20</b> and the support shoulder <b>16</b>.

Advantageously, the support shoulder <b>16</b> rests form fittingly against only part of the end face <b>12</b>. In particular, the support shoulder <b>16</b> covers 10% to 80%, preferably 20% to 60% of the overall area of the end face <b>12</b>. Currently preferred is a coverage of 25% to 50%. Advantageously, the end <b>4</b> of the transverse leaf spring <b>20</b> is not fully encased by the mount <b>50</b>, and the mount <b>50</b> does not embrace the end <b>4</b> of the transverse leaf spring <b>20</b> in its entirety so that the mount <b>50</b> rests only against the underside <b>8</b> and in part against the end face <b>12</b>. The adjacent surfaces are advantageously bonded to one another. Also, the mount <b>50</b> is sized such that no sides of the transverse leaf spring <b>20</b> are embraced.

Adhesive is advantageously applied also between the mount <b>50</b> and the end face <b>12</b>. This results in a self-centering of the mount <b>50</b> upon the transverse leaf spring <b>20</b> and additional stability in motor vehicle Y direction.

<figref idref="DRAWINGS">FIGS. 3<i>a </i>and 3<i>b </i></figref>show installation scenarios of the leaf spring arrangement <b>100</b> according to the invention. In <figref idref="DRAWINGS">FIG. 3<i>a</i></figref>, the end <b>4</b> of the transverse leaf spring <b>20</b> is coupled with the mount <b>50</b> and in kinematic connection with an upper control arm <b>14</b>, e.g. a transverse control arm, via a tie rod <b>13</b>. A force F, exerted by the control arm <b>14</b>, is primarily transmitted upwards through the tie rod, as viewed in the drawing, and causes a compression in the bonded joining surface <b>10</b> between the end <b>4</b> of the transverse leaf spring <b>20</b> and the mount <b>50</b>. Stress for both static and dynamic wheel loads mainly occurs in direction of action of the force F so that the tie rod <b>13</b> predominantly transmits a depicted tensile load, causing a compression in the joining surface <b>10</b>.

<figref idref="DRAWINGS">FIG. 3<i>b </i></figref>shows an arrangement with a lower control arm <b>14</b>, e.g. transverse control arm, which is coupled by a pressure bar <b>15</b>. Thus, a force F is applied via the control arm <b>14</b> predominantly in pressing direction of the pressure bar <b>15</b>, causing again a compression in the joining surface <b>10</b>. Also in this case, the primary force introduction by both static and dynamic wheel loads is established in pressing direction of the pressure bar so that the bond provides sufficient strength and durability between the transverse leaf spring <b>20</b> and the mount <b>50</b> and is easy to implement.

While the invention has been illustrated and described in connection with currently preferred embodiments shown and described in detail, it is not intended to be limited to the details shown since various modifications and structural changes may be made without departing in any way from the spirit and scope of the present invention. The embodiments were chosen and described in order to explain the principles of the invention and practical application to thereby enable a person skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated.